Charged particle beam induced deposition processes such as electron beam induced deposition (EBID) or ion beam induced deposition (IBID) involve the dissociation of surface-adsorbed precursor molecules via electron or ion bombardment. As typically implemented, a gas-phase precursor is delivered through a hollow needle positioned just millimeters from the surface of a substrate located in a high vacuum system. Having formed an adsorbed layer on the substrate surface, the adsorbate-covered surface irradiated by a charged particle beam. As the charged particles cross the substrate-vacuum interface, they transfer some of their energy through inelastic scattering to the precursor molecules adhered to the substrate surface. If the energy transferred is sufficient, molecular bonds are broken and the precursor “dissociates” into stable, solid phase components and volatile by-products. The solid components attach to the surface forming a deposit, thus enabling the direct writing of nanometer to micrometer sized features. This process is typically referred to as deposition. The volatile by-products produced by the dissociation process, subsequently desorb from the substrate and are removed by a pumping system.
It is well known that electron and ion beams can be focused to spot sizes smaller than those achievable with traditional light optics. As a result, the features produced by charged particle beam induced deposition processes can be made smaller than those produced by laser induced processes such as pulsed laser deposition (PLD) and direct-write laser-assisted deposition. However, because E/IBID are relatively slow processes, thick deposits or deposits made over large areas using these techniques can result in long processing times. In addition, the purity of the deposits made with charged particle beam techniques is often low. For deposits that are ideally conductive (e.g. platinum), low purity (e.g. carbon contamination) results in lower than ideal conductivity. In general, contaminant incorporation deteriorates the desired properties of the targeted material for deposition.
There are beam chemistry related references directed toward improvement of purity and/or material properties either through novel processing, post-processing, or novel precursor selection. One such reference describes a novel precursor—hexamethylditin—which can be used to deposit a high purity, low resistivity tin material with IBID. Another is a beam-seeded atomic layer deposition (ALD) technique work where an EBID seed is used to direct the growth via atomic layer depositions via cyclical spontaneous reactions. The result is a pure deposit localized at the catalyst. Both techniques may have drawbacks, however. The tin deposition tends to work only in vias and subsurface features where there is a high degree of gas confinement. The ALD process can be somewhat slow and irreproducible and is subject to problems with vacuum contamination. There are many references for continuous wave and nanosecond pulsed laser induced deposition with both photolytic and pyrolytic mechanisms. But these mechanisms tend to heat the substrate, which can be undesirable.
Accordingly, there is an unmet need for novel high purity deposition processes; in particular there is a need for processes that enable both large and small area deposition of pure metals, dielectrics, and semiconductors.